One of the most basic guitar skills are strumming up and down freely. And I have noticed in songs that there usually appears to be a difference in sounds between the two strokes. But when I'm practicing I don't feel that difference between my strokes. My upstrokes and downstrokes sound more or less the same. Which brings me to my question.

What exactly is the difference between the two strokes, in general, apart from the fact that the pick goes in different directions? Do we alter pressure while doing upstrokes? Or do we trace a curved path touching only few of the strings each time for upstrokes and refrain from playing all the 6 strings? Or do we apply more pressure on the bottommost strings and less on the top ones?

I've always considered downstrokes more powerful because the low notes are hit first. The upstrokes have less power, and are "prettier", or maybe more open. There's definitely a difference between the two.
–
AnonymousJan 22 '11 at 5:25

1

+1 "downstrokes more powerful because the low notes are hit first". Order in which the notes are played is the main thing which separates them soundwise I think; low notes are often not caught as cleanly on the upstroke either, plus perhaps slight differences in pick angle on the upstroke can make a difference(assuming a pick is being used of course)
–
DRLJan 22 '11 at 16:18

3

Many people find it easier to play upstrokes on the off-beat, when "skanking" in styles like reggae or ska. However, The Specials took a trip to Jamaica to learn from the originators of those styles, and were told to use downstrokes because upstrokes sound too weedy.
–
slimNov 11 '11 at 13:23

2

+1 for mentioning that the first hit strings are hit hardest. This is surely the most important, especially if strumming fast. (although you could hit the later strings harder, it definitely wouldn't be as easy...)
–
naught101Sep 19 '12 at 7:31

In an interview in Bass Player Magazine, Jason Newsted talked about how, when he first joined Metallica, James Hetfield insisted he play as much as possible with all downstrokes (until then, he'd played using alternate picking). According to Newsted, Hetfield strongly believed that downstrokes made the rhythm parts sound more powerful, for both bass and guitar, since you could put the whole weight of your arm into it.

For example, the rhythm part on "Master of Puppets" is all downstrokes, which makes it fiendishly more difficult to play than if you use alternate picking. But it sounds heavy and powerful.

Technically there is nothing different, just a slight difference in sound. If you play an upstroke, you are likely to be placing more emphasis on the higher strings, which can be useful in some situations. Playing a downstroke will place more emphasis on the bassier notes, and give good background rhythm while accompanying another player, or recording a song.
Using the two techniques together can create good rhythm to another player, or while playing solo.

This video here provides good information about how to use both techniques to create good strumming patterns.

When strumming quickly, upstrokes and downstrokes are generally not going to sound different on their own, although struming with only one or the other can sound forced and a little robotic. Reasons to use one one or the other:

Convenience: If you're strumming a chord immediately after, say, playing on the higher strings, you'll probably play an upstroke, or moving the pickup switch, since you don't have to move your hand as much. This sort of thing comes into play a lot more when picking individual notes.

Arpeggios, or strumming across the strings very slowly: The downstroke, or from lower to higher notes, is probably more common when playing a single chord. Playing an upstroke in this manner can sound a little odd and out of place, and this is often used for effect.

My first guitar teacher always tried to convince me volume was the difference, because we somehow had the help of gravity on the way down. I changed guitar teachers shortly thereafter.

In my opinion, the differences are almost always purely tonal quality due to the higher strings being set in motion first. I have very little knowledge of acoustics, but I suspect the sympathetic vibrations of the other strings before you hit them also have something to do with the resulting tone. As a result the upstrokes will have a somewhat lighter feel than the downstrokes. HOWEVER: I believe that it depends on what style you're playing in, how fast you're strumming, how many upstrokes there are where there "should" be downstrokes, etc. I think that a good guitar player, can, in many styles, use his/her choice of strum and still make it sound as desired. Depends on a million different musical aspects of course; hard rock would be more difficult to work it. Light strumming on an acoustic guitar in a quick folk-style song would be easier.

This is my experience as a musician and music educator, not as a professional guitarist, so your mileage may vary. I'd say a general rule would be to use whatever combination results in the sound required without being too difficult or detracting from other elements. If playing all downstrokes even slightly changes the regularity of the pattern, then (in my opinion) you should alternate and focus on getting an even-ness of sound.

+1 From my musical acoustic studies I learnt that the attack of a musical sound is very important for how the sound is perceived. A piano attack with a violin sustain will (largely) be percieved as a piano note, and a violin attack with a piano sustain will (largely) be perceived as a violin note. The guitar attack of an upstroke will always be different than the attack of a downstroke at the very least due to the order of the strings. Thus the sound will be perceived as different.
–
Ulf ÅkerstedtJul 20 '13 at 19:46

There's also an angular difference in how the pick hits the strings. It seems like this ..

If the wrist is doing some of the work, then it must flex, so as you strum downwards the angle that the pick hits the strings is different to on the way back up.

I guess we have our individual styles so I can't predict what the actual difference is, but if your down and upstroke sound the same, maybe you're holding the wrist a bit tense ? Not that there's really a "Right or Wrong". Whatever works for you :-)

I tend to kind of flop my wrist slighlty as strumming down, and opposite again on the way back up (not an exact science .. very human floppy kind of movement), so on the way back up I think the pick hits the strings at more of an off-angle so it's kind of riding over the strings using the rounded part of the pick, wheras on the way down it's more hitting the strings (almost) flat-on. That woudl account for a very different sound.

I've just got some strange looks from practicing this movement while sitting at the computer.

I didn't notice until AFTER I posted an answer that you had resurrected this question from 4 years ago. But I think we both added some valuable content. Thanks for putting it back on the radar.
–
Rockin CowboyMar 16 at 18:09

I agree with pretty much everything said so far. But want to add that the difference in sound actually goes beyond which strings are emphasized. A big part of the difference in sound is which strings are omitted in the up strum.

In basic rhythm guitar playing (which strumming usually is) our strumming serves to establish a certain rhythmic feel to the song. In most cases, the upstrokes are part of keeping a consistent rhythm and the consistency part is best accomplished by establishing a pendulum type movement with your wrist. Hitting the strings on the up strum is often a part of establishing the rhythm pattern and feel of many songs - in which case you will want to strum some strings on the up strum as well as the down strum.

When doing this type down-up strumming, the natural arc of your strum will result in you missing some of the bass strings on the upstroke. This is normal, acceptable and common. I find that I have to make a conscious effort to play the low E string or A string on an upstroke as part of a down-up strumming pattern. And if I do make this conscious effort, it disrupts the rhythmic pendulum action of my wrist.

There are certainly situations in some songs where an intentional full up strum is part of the arrangement (often a slower rake), but you really have to slightly alter your normal up-strum to accomplish this. I usually do this type intentional full up strum with more upward movement in my forearm as opposed to just the wrist.

So in most rhythmic strumming patterns, your up strum will miss the bass notes of the chord your are holding and thus will sound a little thinner for that reason alone (in addition to other reasons mentioned). In most cases the accent beats will be emphasized by using a down strum. In other words if your were counting One and Two and Three and Four and .... - the up-strums would be on the ands. That's why it's actually a good thing that the natural arc of an up-strum results in playing fewer strings. The exceptions require conscious thought and alteration in your normal strum.